Session 9 Flashcards Preview

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Flashcards in Session 9 Deck (33)
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1
Q

What is Pharmacokinetics?

A

What the body does to a drug

2
Q

What are the 2 formulations of a drug?

A

Solid

Liquid

3
Q

If the drug is a solid, what does rate of action depend on?

A

Dissolution

4
Q

What are the sites of administration?

A

Local (eg oral, rectal)

Systemic - Enteral (Sublingual) Parenteral (IV, inhalation)

5
Q

What is the advantage of local administration of drugs?

A

There are high concentrations of the drug at the site

There are less systemic effects

6
Q

What is Oral Bioavailability?

A

Proportion of dose given orally (or any other route except IV) that reaches the systemic circulation in an unchanged form

7
Q

How can Bioavailability be expressed?

A

Amount

Rate

8
Q

How can you calculate the Bioavailability of a drug?

A

Area under curve for oral /
Area under curve for injection
x100

9
Q

What is the Therapeutic ratio?

A

Maximum tolerated dose (L50) /

Minimum effective dose (ED50)

10
Q

Is a low or high Therapeutic ratio desirable?

A

High because this means the desired curve is far from the side effects curve

11
Q

What is the First Pass effect?

A

A substance absorbed through the Ileum will enter the venous blood and passes directly to the liver where it is extensively metabolised before reaching the rest of the body.

12
Q

Which routes can avoid the First Pass effect?

A

Parenteral
Sublingual
Rectal

13
Q

What is Drug Distribution?

A

Theoretical volume into which a drug has distributed assuming that this occurs instantaneously

14
Q

How can you calculate Drug Distribution?

A

Amount given /

Plasma concentration at time 0

15
Q

What exerts the effects of a drug?

A

The level of free drug in the blood

16
Q

What is the main plasma protein that drugs can bind to?

A

Albumin

17
Q

When are protein binding actions important?

A

Drugs highly bound to albumin
Drug have a small volume of distribution
Drug has low therapeutic index

18
Q

What is an Object (Class I) drug?

A

It is the drug that is medically active. It is used at a concentration which is much lower than the number of albumin binding sites

19
Q

What is a Precipitant (Class II) drug?

A

The drug that is used at higher concentrations (Than the available binding sites) to displace the Class I drug from albumin.

20
Q

What is the precipitant drug for Warfarin?

A

Aspirin

Sulphonamides

21
Q

What is First order Kinetics?

A

The metabolism of the drug is proportional to drug concentration. Half life can be defined.

22
Q

What would you see on a graph for First order Kinetics?

A

A straight line when a log scale is on the Y axis Vs time.

23
Q

What is Zero order Kinetics?

A

Rate of elimination is constant regardless of concentration.

24
Q

What would you see on a graph for Zero order Kinetics?

A

Straight line when normal (not log) plasma concentration is plotted against time (X)

25
Q

How many half lives does it take for drug to reach a steady state?

A

5 half lives for all drugs regardless of dose or frequency

26
Q

What is needed for an immediate effect of a drug?

A

A loading dose

27
Q

How can you determine the loading dose?

A

Volume of distribution

28
Q

What is the difference between First order Kinetics and Zero order kinetics?

A

First order gives a predictable Therapeutic response from dose increases
Zero order kinetics give a therapeutic response that can suddenly escalate as elimination mechanism saturate

29
Q

What are some examples of Cytochrome P450 enzyme inducers?

A

Cigarettes (effects Theophylline drug)

Rifampicin (effects OC pill)

30
Q

What is an example of Cytochrome P450 enzyme inhibitors?

A

Cimetidine (effects Warfarin drug)

31
Q

What can be filtered through the Glomerulus in the Kidneys?

A

Free unbound drugs only

32
Q

What can cause weak acids to be excreted more in the kidneys?

A

Making the urine alkaline because it will make the drug remain ionised to it will be excreted

33
Q

What can cause weak bases to be excreted more in the kidneys?

A

Acidic urine will increase excretion as it will ionise the weak base